1. Field of the Invention
The invention relates to aircraft gas-turbine engine thrust-reversers and more particularly to thrust reversers especially designed to allow visual monitoring on the ground of the lock-status of the reverser shutter.
2. Related Technology
Aircraft thrust-reversers are well known equipment to reverse the thrust gas or air flows generated by gas-turbine engines powering the aircraft to decelerate the aircraft.
Thrust reversers typically are integrated with an an annular structure or cowling enclosing the gas-turbine engine. This annular structure in turn comprises a first portion or fixed structure which includes a plurality of radial apertures and a second portion consisting of at least one displaceable shutter device or door to close the radial apertures. When the radial apertures are closed, the thrust flow generated by the gas turbine engine is channeled rearwardly to propel the aircraft. When the radial apertures are open, the thrust flow passes through said apertures and is directed forwardly to decelerate the aircraft. High reliability is required for keeping the shutters in their closed position. Accordingly each shutter is kept closed by at least one main locking system and at least one emergency locking system, the purpose of the latter being to keep the shutter closed in spite of a failure in the main locking system. The expression "locking system" denotes a lock mounted on one part of the reverser assembly and cooperating with a lock-interfacing means mounted on another part of the reverser assembly. Usually, but not necessarily, the lock is mounted on the fixed structure and the lock-interfacing means is mounted on the shutter.
The typical annular thrust-reverser structure is radially bounded by two thin walls, namely an inner wall channeling the thrust flow and an outer wall exposed to the ambient air. These walls are interconnected by frame elements to achieve, with low weight, both thrust-reverser rigidity and structural integrity. Typically the locking systems are mounted on the bracing or frame elements for the fixed structure and the shutters.
Monitoring the appropriate locking of the shutters is based on electric detection and signaling means associated with the mechanical components controlling the locking procedure. The electric area signaling means themselves may malfunction or transmit spurious locking signals. Accordingly, a dangerous situation may arise which cannot be detected when the aircraft is on the ground and about to take off, namely when the shutters may be closed but unlocked. The problem is to reliably signal the closed mode of the locking means while the aircraft is on the ground.